More than 400 people have died in jihadist attacks in the West during the past three years. What can we learn?

More than 400 people have died in jihadist attacks in the West during the past three years. What can we learn, asks Dr Lorenzo Vidino.

Although the vast majority of Islamist attacks are elsewhere in the world, an unprecedented number in Europe and North America - more than 50 in total - have put the authorities under great pressure to prevent further deaths.

Although the vast majority of Islamist attacks are elsewhere in the world, an unprecedented number in Europe and North America - more than 50 in total - have put the authorities under great pressure to prevent further deaths.

What do we know of the individuals who carried out the attacks - their life in the West, whether they were known to the authorities and with whom they were working?

What do we know of the individuals who carried out the attacks - their life in the West, whether they were known to the authorities and with whom they were working?

The first look at the data behind the attacks - everything from the age of the perpetrators, to immigration status - offers counter-terrorism officials, and the public, an insight that could help them identify the best responses.

The first look at the data behind the attacks - everything from the age of the perpetrators, to immigration status - offers counter-terrorism officials, and the public, an insight that could help them identify the best responses.

Where the attacks were

Where the attacks were

We identified 52 attacks between December 2014 and early June 2017 that we considered to be acts of jihadist terrorism.

We identified 52 attacks between December 2014 and early June 2017 that we considered to be acts of jihadist terrorism.

This period follows the declaration of a "caliphate" by the so-called Islamic State in parts of Syria and Iraq in June 2014.

This period follows the declaration of a "caliphate" by the so-called Islamic State in parts of Syria and Iraq in June 2014.

A relatively limited number of countries were affected.

A relatively limited number of countries were affected.

Six were in Europe: France - the worst affected country, Germany, the United Kingdom, Belgium, Denmark and Sweden.

Six were in Europe: France - the worst affected country, Germany, the United Kingdom, Belgium, Denmark and Sweden.

There were also attacks in the United States and Canada.

There were also attacks in the United States and Canada.

Regardless of country, most attacks were in large towns and cities - including London, Paris, Nice, Berlin, Brussels and Orlando.

Regardless of country, most attacks were in large towns and cities - including London, Paris, Nice, Berlin, Brussels and Orlando.

A few attacks hit iconic targets, such as the Champs-Elysees and the Louvre museum in Paris, and Westminster in London.

A few attacks hit iconic targets, such as the Champs-Elysees and the Louvre museum in Paris, and Westminster in London.

But some terrorist attacks have hit more unusual places, including an office Christmas party and a service at a church.

But some terrorist attacks have hit more unusual places, including an office Christmas party and a service at a church.

How the attacks were identified

How the attacks were identified

We looked at attacks motivated by jihadist ideology, that involved deliberate acts of violence against other people and were intended to intimidate or convey a message to a larger group. Other organisations use different definitions.

We looked at attacks motivated by jihadist ideology, that involved deliberate acts of violence against other people and were intended to intimidate or convey a message to a larger group. Other organisations use different definitions.

The dead and injured

The dead and injured

In total, the 52 attacks caused 403 deaths and left more than 1,600 people injured.

In total, the 52 attacks caused 403 deaths and left more than 1,600 people injured.

The perpetrators are not included in these figures.

The perpetrators are not included in these figures.

The Paris attack of November 2015 was the deadliest, with 130 people killed, including 90 at the Bataclan theatre.

The Paris attack of November 2015 was the deadliest, with 130 people killed, including 90 at the Bataclan theatre.

France also saw the Nice lorry attack, which left 86 people dead.

France also saw the Nice lorry attack, which left 86 people dead.

There were many other attacks that left many people dead and others injured.

There were many other attacks that left many people dead and others injured.

In total, these 10 attacks were responsible for 370 deaths.

In total, these 10 attacks were responsible for 370 deaths.

However, most of the attacks did not cause casualties, with the exclusion of the perpetrators.

However, most of the attacks did not cause casualties, with the exclusion of the perpetrators.

Who the attackers were

Who the attackers were

Although the number of young people being radicalised has caused concern, the average age of the attackers - 27 - is not unusually young.

Although the number of young people being radicalised has caused concern, the average age of the attackers - 27 - is not unusually young.

The two youngest were 15 - an unnamed boy who attacked a Jewish teacher with a machete in Marseille, and Safia S, a girl who stabbed a police officer at a Hannover train station.

The two youngest were 15 - an unnamed boy who attacked a Jewish teacher with a machete in Marseille, and Safia S, a girl who stabbed a police officer at a Hannover train station.

Of the five who were under the age of 18 at the time, four were in Germany.

Of the five who were under the age of 18 at the time, four were in Germany.

The vast majority of the attackers were in their 20s, with about one in four attackers above the age of 30 and three aged 40 or older.

The vast majority of the attackers were in their 20s, with about one in four attackers above the age of 30 and three aged 40 or older.

The oldest attacker, Khalid Masood, was 52 when he drove into pedestrians on Westminster Bridge and stabbed to death a police officer at the Houses of Parliament.

The oldest attacker, Khalid Masood, was 52 when he drove into pedestrians on Westminster Bridge and stabbed to death a police officer at the Houses of Parliament.

It is noteworthy that the older perpetrators were twice as likely to have been imprisoned and to have a history of substance abuse.

It is noteworthy that the older perpetrators were twice as likely to have been imprisoned and to have a history of substance abuse.

Despite women becoming increasingly active in jihadist networks, only two out of 65 individual perpetrators were female.

Despite women becoming increasingly active in jihadist networks, only two out of 65 individual perpetrators were female.

Fewer than one in five perpetrators was a convert to Islam, with a significantly higher percentage in North America than in Europe.

Fewer than one in five perpetrators was a convert to Islam, with a significantly higher percentage in North America than in Europe.

However, the converts were significantly more likely to have a criminal background and to have served time in prison.

However, the converts were significantly more likely to have a criminal background and to have served time in prison.

Overall, most of the attackers had a prior criminal background.

Overall, most of the attackers had a prior criminal background.

Immigration status

Immigration status

The relationship between terrorism and migration is a complex one and has been at the centre of extremely polarising debates, particularly during the European migrant crisis.

The relationship between terrorism and migration is a complex one and has been at the centre of extremely polarising debates, particularly during the European migrant crisis.

However, the number of attackers who were illegally in a country or who arrived as refugees is small.

However, the number of attackers who were illegally in a country or who arrived as refugees is small.

Three-quarters were citizens of the country they attacked, with others either legal residents, or legal visitors from neighbouring countries.

Three-quarters were citizens of the country they attacked, with others either legal residents, or legal visitors from neighbouring countries.

However, individuals who were in the West illegally also carried out deadly attacks.

However, individuals who were in the West illegally also carried out deadly attacks.

At least two of those involved in the November 2015 Paris attacks are thought to have posed as refugees to enter Europe through Greece.

At least two of those involved in the November 2015 Paris attacks are thought to have posed as refugees to enter Europe through Greece.

Three other individuals were refugees or asylum seekers at the time of attack, while four were in the country illegally or awaiting deportation.

Three other individuals were refugees or asylum seekers at the time of attack, while four were in the country illegally or awaiting deportation.

The latter group includes Uzbek national Rakhmat Akilov, who killed four people with a hijacked lorry in Stockholm in April 2017, and Tunisian citizen Anis Amri, who also used a lorry to commit his attack at the Berlin Christmas market.

The latter group includes Uzbek national Rakhmat Akilov, who killed four people with a hijacked lorry in Stockholm in April 2017, and Tunisian citizen Anis Amri, who also used a lorry to commit his attack at the Berlin Christmas market.

There is also one case of "terrorist tourism", involving Egyptian citizen Abdullah Hamamy, who lived in the United Arab Emirates and attacked soldiers at the Louvre in February 2017.

There is also one case of "terrorist tourism", involving Egyptian citizen Abdullah Hamamy, who lived in the United Arab Emirates and attacked soldiers at the Louvre in February 2017.

Links to IS

Links to IS

Two of the four most lethal attacks - those in Paris in November 2015 and in Brussels in 2016 - are believed to be well orchestrated multiple attacks directed by IS.

Two of the four most lethal attacks - those in Paris in November 2015 and in Brussels in 2016 - are believed to be well orchestrated multiple attacks directed by IS.

They were also executed in part by former foreign fighters.

They were also executed in part by former foreign fighters.

However, the two other most deadly attacks - those in Orlando in June 2016 and in Nice in July 2016 - were carried out independently by individuals without operational connection to a jihadist group.

However, the two other most deadly attacks - those in Orlando in June 2016 and in Nice in July 2016 - were carried out independently by individuals without operational connection to a jihadist group.

These episodes demonstrate that terrorist sympathisers who never travelled to conflict areas and who act independently can be as dangerous as a team of highly trained militants.

These episodes demonstrate that terrorist sympathisers who never travelled to conflict areas and who act independently can be as dangerous as a team of highly trained militants.

Overall, links between attackers and jihadist groups operating overseas are not always easy to determine.

Overall, links between attackers and jihadist groups operating overseas are not always easy to determine.

Of the attacks that have hit the West since June 2014, fewer than one in 10 was carried out under direct orders from the leadership of IS.

Of the attacks that have hit the West since June 2014, fewer than one in 10 was carried out under direct orders from the leadership of IS.

Nevertheless, the influence of IS can be clearly seen.

Nevertheless, the influence of IS can be clearly seen.

During or before the attack, six out of 10 perpetrators pledged allegiance to a jihadist group, almost always IS - which frequently claims responsibility.

During or before the attack, six out of 10 perpetrators pledged allegiance to a jihadist group, almost always IS - which frequently claims responsibility.

Learning the lessons

Learning the lessons

Unsurprisingly, given the frequency of attacks and the number of deaths and injuries, jihadist terrorism has come to the fore of political debates in the West and receives widespread news coverage.

Unsurprisingly, given the frequency of attacks and the number of deaths and injuries, jihadist terrorism has come to the fore of political debates in the West and receives widespread news coverage.

The threat is not expected to wane in the near future, with policymakers, counter-terrorism officials and the public all being asked to take action.

The threat is not expected to wane in the near future, with policymakers, counter-terrorism officials and the public all being asked to take action.

There are huge implications for domestic and foreign policy throughout Western countries.

There are huge implications for domestic and foreign policy throughout Western countries.

It is hoped that knowing more about the attacks and the people who carried them out will help us all have a more informed debate about what action is needed.

It is hoped that knowing more about the attacks and the people who carried them out will help us all have a more informed debate about what action is needed.

About this piece

About this piece

This analysis piece was commissioned by the BBC from an expert working for an outside organisation.

This analysis piece was commissioned by the BBC from an expert working for an outside organisation.